The long-term objective of this proposal is to understand the pathophysiological processes and molecular interactions that lead to cellular dysfunction and neurotoxic vulnerability with aging, injury, and disease. Human pluripotent stem cells and their differentiated progeny are an ideal paradigm to address these concerns because they can be used to generate fate-committed cells in the cortex that are either resistant or susceptible to neurodegenerative disease (NDD). Methods to generate and enrich for cortical inhibitory interneurons and cortical excitatory projection neurons from human pluripotent stem cells were developed during the K99 phase. The central hypothesis to be tested in this proposal is that cortical projection neurons (CPN) exhibit pathophysiological features and molecular interactions that lead to their dysfunction and death with NDD progression. This hypothesis will be tested in the R00 phase through experiments that: 1) determine the non-cell autonomous role that glial cells play in promoting neuroinflammation and conferring toxicity onto neuronal subpopulations and 2) identify the intrinsic molecular cascades that render NDD patient-derived CPN vulnerable to dysfunction and death. Successful completion of the proposed experiments will significantly advance our understanding of the molecular pathways and cellular interactions that induce or exacerbate functional decline with aging and NDD susceptibility. Furthermore, the assays in this proposal will identify pathogenic phenotypes that lead to the development of novel therapeutic targets at distinct stages of NDD progression.